1. Field of the Invention
The present invention relates to a touch screen apparatus, and more particularly, to a touch screen apparatus capable of eliminating ghost points and determining the coordinate pair of an accurate touch point when two or more touch points are present within a touch area.
2. Description of the Related Art
In general, a touch screen is applied to a personal mobile terminal, such as a mobile phone or a PDA, and also applied to a field in which a touched location (i.e. pointed location) in a wide area, such as a large screen or a black board is indicated as coordinates. Detecting the coordinates of a touch on a small touch screen is realized through detecting the pressure of a touch or the change of capacitance because of the touch. However, a large touch screen is realized through calculating the coordinates of a point from which no reflected light is received during irradiating light to a touched area and receiving the irradiated light.
A large touch screen apparatus in the related art has a structure in which retroreflectors are provided on the continuous three sides of a quadrilateral touch area and light transmitting and receiving parts are disposed at the ends of the continuous three retroreflectors, respectively. Here, each of the light transmitting and receiving part irradiates light to the touch area and receives reflected light through a path identical to that of the light irradiated by the retroreflectors. This large touch screen apparatus in the related art, when a pointed location is present within the touch area, may detect where the pointed location is situated because the light transmitting and receiving parts fail to receive the reflected light from the irradiated light. Therefore, angles detected by the two light transmitting and receiving parts with respect to one reference line are obtained, thereby calculating the coordinate pair of the pointed location.
However, in this general large touch screen apparatus, when two or more pointed locations are present within the touch area, a plurality of angles are detected by each of the light transmitting and receiving parts. Thus, when the angles detected by the two light transmitting and receiving parts are combined, coordinate pairs which do not indicate actual pointed locations (i.e. ghost coordinate pairs) may be caused.
In the touch screen apparatus in the related art, there is provided no solution capable of solving the defect of the ghost coordinate pairs caused when the plurality of pointed locations are present within the touch area. Thus, there is a limitation that a user needs to use only one pointed location.
Therefore, a technique capable of confirming and eliminating the ghost coordinate pairs caused when a plurality of pointed locations, particularly two pointed locations, are present within the touch area is required in the art.